Java Date & Time

Java's date and time tools let a program work with dates, clock times, and gaps between them, like a calendar and clock combined. You can add days, format them, or find how long between two dates.

In this page:

LocalDate and LocalTime
LocalDateTime
Formatting Dates
Modifying Dates
Duration and Period

Syntax

java

import java.time.*;

LocalDate date = LocalDate.now();
LocalDateTime dateTime = LocalDateTime.of(year, month, day, hour, minute);

LocalDate and LocalTime

LocalDate represents a calendar date with no time component, and LocalTime represents a time of day with no date — use whichever matches what you're actually modeling.

Example: LocalDate and LocalTime

java

// Import java.time.LocalDate so it can be used by its short name
import java.time.LocalDate;
// Import java.time.LocalTime so it can be used by its short name
import java.time.LocalTime;
// Define the class Main
public class Main {
	// Program entry point: the JVM starts running here
	public static void main(String[] args) {
		LocalDate date = LocalDate.of(2024, 1, 15);
		LocalTime time = LocalTime.of(14, 30);
		// Print a line to the console
		System.out.println(date);
		// Print a line to the console
		System.out.println(time);
	}
}

LocalDateTime

LocalDateTime combines both into a single date-and-time value, useful for representing a specific moment without needing timezone information attached.

Example: LocalDateTime

java

// Import java.time.LocalDateTime so it can be used by its short name
import java.time.LocalDateTime;
// Define the class Main
public class Main {
	// Program entry point: the JVM starts running here
	public static void main(String[] args) {
		LocalDateTime dt = LocalDateTime.of(2024, 1, 15, 14, 30);
		// Print a line to the console
		System.out.println(dt);
	}
}

Formatting Dates

DateTimeFormatter controls how a date or time is rendered to a string (and parsed back from one), letting you match locale-specific or application-specific formatting requirements.

Example: Formatting Dates

java

// Import java.time.LocalDate so it can be used by its short name
import java.time.LocalDate;
// Import java.time.format.DateTimeFormatter so it can be used by its short name
import java.time.format.DateTimeFormatter;
// Define the class Main
public class Main {
	// Program entry point: the JVM starts running here
	public static void main(String[] args) {
		LocalDate date = LocalDate.of(2024, 1, 15);
		DateTimeFormatter fmt = DateTimeFormatter.ofPattern("dd/MM/yyyy");
		// Print a line to the console
		System.out.println(date.format(fmt));
	}
}

Modifying Dates

Because these classes are immutable, methods like plusDays() or minusMonths() return a *new* date/time object rather than modifying the original — you must capture the return value to see the change.

Example: Modifying Dates

java

import java.time.LocalDate;
public class Main {
	public static void main(String[] args) {
		LocalDate date = LocalDate.of(2024, 1, 15);
		LocalDate later = date.plusDays(10); // new object, original unchanged
		System.out.println(date);
		System.out.println(later);
	}
}

Duration and Period

Duration measures a span of time in seconds/nanoseconds (for time-based values), while Period measures a span in years/months/days (for date-based values) — pick based on what unit actually makes sense for your calculation.

Example: Duration and Period

java

// Import java.time.Duration so it can be used by its short name
import java.time.Duration;
// Import java.time.Period so it can be used by its short name
import java.time.Period;
import java.time.LocalDate;
// Define the class Main
public class Main {
	// Program entry point: the JVM starts running here
	public static void main(String[] args) {
		Duration duration = Duration.ofMinutes(90);
		Period period = Period.between(LocalDate.of(2024, 1, 1), LocalDate.of(2024, 3, 1));
		// Print a line to the console
		System.out.println(duration);
		// Print a line to the console
		System.out.println(period);
	}
}

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Java Date & Time

LocalDate and LocalTime

LocalDateTime

Formatting Dates

Modifying Dates

Duration and Period

Chapter Quiz — Complete all 10 topics to unlock

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